Many Cantonese like it blanched, served at room temperature with a simple green onion & ginger with light soy sauce as dressing on the side, or sometimes with XO sauce as condiment.

But you'll also see it stir-fried with snowpea pods.

Or in Chinese hotpot, geoduck is cut thin and served cold sashimi-style on a bed of ice. You then cook it yourself in the hotpot.

Geoduck is easy to overcook, and it's mildly sweet flavour lends itself to (Chinese) cooking methods that don't introduce heavy flavours, such that its original flavours are preserved. I've eaten it stir-fried with blackbean suace and while some people like that, I don't personally. Guess I'm a Canto-boy at heart, I like it best the blanched way.